1. Field of the Invention
The invention relates to a high-pressure fuel reservoir for a common rail fuel injection system of an internal combustion engine, with a number of fittings for fuel lines.
2. Description of the Prior Art
In common rail injection systems, a high-pressure fuel pump, possibly with the aid of a presupply pump, supplies the fuel to be injected from a tank to the central high-pressure fuel reservoir, which is referred to as the common rail. Fuel lines lead from the rail to the individual injectors which are associated with the cylinders of the internal combustion engine. The injectors are individually triggered by the engine electronics as a function of the operating parameters of the engine in order to inject fuel into the combustion chamber of the engine. The pressure production and the injection are decoupled from each other by the high-pressure fuel reservoir.
A conventional high-pressure fuel reservoir is described, for example, in DE 195 48 611. The known high-pressure fuel reservoir is comprised of an elongated, tubular body with a number of connections for supplying injectors. The ends of the fuel lines can only move to a limited degree in the fittings of the high-pressure fuel reservoir. The lack of mobility of the fuel lines in the fittings of the high-pressure fuel reservoir turns out to be disadvantageous during installation of the high-pressure fuel reservoir in the engine.
The object of the invention is to embody a high-pressure fuel reservoir of the type described at the beginning so that the ends of the fuel lines are sufficiently mobile in the fittings. Despite the sufficient mobility, the seal at these fittings should also be assured at high pressures. In addition, the high-pressure fuel reservoir according to the invention should be simple in design and inexpensive to produce.
In a high-pressure fuel reservoir for a common rail fuel injection system of an internal combustion engine with a number of fittings for fuel lines, the object is attained by virtue of the fact that an intermediary piece is disposed in each of the fittings between the high-pressure fuel reservoir and the fuel lines. The mobility of the fuel lines in the fittings is improved considerably by means of the intermediary piece. Manufacturing-and assembly-related tolerances can be compensated for by the improved mobility.
One particular embodiment of the invention is characterized in that the intermediary piece is essentially the shape of a hollow cylinder with two conical end faces which cooperate with complementary end faces in the fuel line and in the high-pressure fuel reservoir. The conical end faces produce a favorable sealing action when the complementary end faces are braced against each other.
Another particular embodiment of the invention is characterized in that an external thread is provided on the fitting, which cooperates with the internal thread of a securing nut so that the fuel line is braced with its free end against the intermediary piece and the intermediary piece is braced against the high-pressure fuel reservoir. The securing nut permits the fuel lines to be rapidly mounted onto the high-pressure fuel reservoir.
Another particular embodiment of the invention is characterized in that the end of the intermediary piece oriented toward the high-pressure fuel reservoir and the end of the intermediary piece oriented away from the high-pressure fuel reservoir are tapered and that a radial support surface for the fuel line is embodied on the securing nut. The symmetrical embodiment of the intermediary piece simplifies its installation because the installer does not have to pay attention to the orientation of the intermediary piece as it is inserted into the fitting.
Another particular embodiment of the invention is characterized in that the end of the intermediary piece oriented toward the high-pressure fuel reservoir is tapered, that the end of the intermediary piece oriented away from the high-pressure fuel reservoir is funnel-shaped, and that the intermediary piece is supported with at least a part of its external circumferential surface against the internal circumferential surface of the fitting. If the intermediary piece has an asymmetrical shape, then on the end face oriented toward the fuel line, it could be stretched open by the complementary end face of the fuel line. Such a stretching open is prevented by the fact that the intermediary piece is supported with at least a part of its outer circumferential surface against the inner circumferential surface of the fitting.
Another particular embodiment of the invention is characterized in that the fittings are welded onto the high-pressure fuel reservoir. This embodiment offers the advantage that the seal in relation to the outside is produced directly at the high-pressure fuel reservoir. The intersecting point between the fitting and high-pressure fuel reservoir does not have to be designed as high-pressure-tight. This reduces manufacturing costs.